MacBook pro is stuck at 50% loading bar after restart

[iMore Question]

I restarted my MacBook pro after an update to OS X and after I typed in my password, it displayed a loading (progression) bar and it's been stuck at 50% for about 5 days now. I've tried the safe-mode boot, no luck. Re-installing OS X, no luck (it says there's an error with the installation and I should try again).

 

[Bigeric23]

I would attempt another install, and if that does not work, I would contact Apple for assistance.